One of the trends in the packaging industry is towards down-gauging or reducing the gauge of plastic film used in household film applications such as trash bags. While this reduces the waste going into landfills, it results in several annoyances to the consumer.
Thinner bags have a lower strength (impact, tear, puncture, and tensile). Additionally, thinner bags may lack stiffness which permits the bag to be opened easily. Accordingly, it would be desirable to have bags with improved stiffness without a significant loss of strength (such as impact, tear, tensile, and puncture resistance).
Accordingly, there is a need for a polymer alloy suitable for use in thin gauge films having good stiffness without a loss in strength such as impact, puncture and/or tear resistance.
There have been a number of approaches to try to overcome the drawbacks noted above. Generally, the approach has been to blend a polyolefin with a stiffer rigid polymer, typically a styrenic polymer. Unfortunately, most of these rigid polymers are not compatible with polyolefins. Accordingly, a small amount of compatibilizer is added to the blend. Desirably the compatibilizer would be a polymer having a styrenic component and an olefin or at least an aliphatic component. Given this desiderata, the first approach was to blend styrene butadiene styrene block polymers (SBS) or hydrogenated styrene butadiene styrene (also called styrene-ethylene-butene or butylene-styrene (SEBS)) copolymers into the alloy. This approach is illustrated by a number of patents including U.S. Pat. Nos. 4,386,186 and 4,386,187, issued May 31, 1983, assigned to Sweetheart Plastic Inc.; Canadian Patent 1,104,741, issued Jul. 7, 1981, assigned to The General Electric Company; and French Patent No. 2,356,694, published Jan. 27, 1978 in the name of Siamp-Cedap Reunies.
Applicant has conducted a number of patent searches and has been unable to locate any art relating to alloys of the present invention and particularly alloys containing a C.sub.4-8 polyolefin in conjunction with a copolymer of ethylene and a C.sub.1-4 alkyl ester of a C.sub.3-6 ethylenically unsaturated carboxylic acid and a rigid polymer.